Sarthak and Mohan are working on alternate days in a workshop. Sarthak can complete the work in 20 days while Mohan can finish in 25 days. Sarthak works on the 1st day, Mohan on the 2nd day, and so on. How much time (in days) will they take on alternate basis?
Show answer & explanation
Correct answer: B
Explanation
The correct answer is Option 2 i.e. .
Work done by Sarthak in 1 day = 1/20
Work done by Mohan in 1 day = 1/25
Combined work in 2 days = (1/20) + (1/25)
⇒ Combined work in 2 days = (5 + 4) / 100
⇒ Combined work in 2 days = 9/100
Total work = 1
Number of such 2 day cycles required to complete the work = Total work / Combined work in 2 days
⇒ 1 / (9/100)
⇒ 100/9 ≈ 11 cycles
Work done in 11 cycles or 22 days = 11 × 9/100 = 99/100
Remaining work = 1 - 99/100 = 1/100
Now, Sarthak complete this work in 20/100 = 1/5.
Total days = 22 1/5.